No public key to verify signature

[gabrix]

I run debian etch and kmail is my mail application.
All mail i get signed by gnupg coming from mailing lists , has this error:

"Message was signed on 2008-06-03 14:15 with unknown key 0x123456789ABCDFGH.
The validity of the signature cannot be verified.
Status: No public key to verify the signature"

It doesn't happen with other mail coming from my contacts or friends i was 
wondering what it was due this error , thanks
-- 
#######################################################################
Email: root at gabrix.ath.cx

MSN:   sickuser at gmail.com

Ekiga: gabrihell at ekiga.net

Skype: gabx666

jabber: gabrihell at jabber.linux.it



My Gnupg pub key : https://www.gabrix.ath.cx/mynewpubkey.asc
--------------------------------------------------------------
sec   1024D/6C71F528 2008-03-18
      Key fingerprint = AD40 8FC1 F8C0 60E1 608E  C136 8080 9773 6C71 
F528
uid                  Gabriele (PRIMA NUOVA SERIE) <gabrix at gabrix.ath.cx>
ssb   4096g/63E0E427 2008-03-18



------------------------------------------------------------------------
                           |  .''`.  ** Debian GNU/Linux **
      Gabriele S.          | : :' :      The  universal
https://www.gabrix.ath.cx/ | `. `'      Operating System
                           |   `-    http://www.debian.org/

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